The basic escape and ventilating hatch mechanism to which the present invention relates is shown in predecessor U.S. Pat. No. 4,021,073 entitled "COMBINED VENT AND ESCAPE HATCH". U.S. Pat. No. 4,495,731 represents an improvement over the early patent in providing a plastic hatch supporting ring adapted to be mounted directly to the vehicle roof. The later patent enabled the more accurate and easier mounting of the hatch assembly and further facilitated the use of an interior trim molding providing a more finished appearance to the hatch assembly.
Hatch assemblies made in accordance with the teachings of the two previously mentioned patents have become the industry standard and are extensively used on buses throughout the world. However, through an unexpected use of such hatches, or what might better be called a misuse, damage to the hinge and connecting linkages may result. One way the problem can begin is when maintenance personnel use the emergency unlatching mechanism to open the hatch so that they can have access to the exterior roof of the vehicle for vehicle maintenance purposes. When such personnel are finished using such hatch for maintenance purposes, they may simply close the hatch without re-latching it. Thereafter when the vehicle is driven the hatch can bounce open or be opened by the force of the wind and thereby cause the supporting hinge and attaching linkages to become severely damaged.
Another way such damage can occur is when the hatch is raised to its maximum ventilating position, wherein the hatch is parallel to the roof, and when in such raised or elevated position the vehicle is driven under or through an obstruction which contacts the hatch causing the hatch supporting hinge and attaching linkages to be damaged.
A related problem can also arise in the case where even though the hinge is damaged but the hatch is not and the user attempts to substitute an unapproved replacement hinge which can result in the ultimate inoperativeness of the hatch assembly either for escape or ventilation purposes.
It is the purpose of the present invention to provide a new and improved hatch supporting assembly which will essentially prevent the hatch from being inadvertently damaged due to the application of unanticipated and excessive opening forces to the hatch.